When graphene serves as a saturable absorber, it can generate two types of mode-locking states

https://phys.org/news/2023-07-graphene-saturable-absorber-generate-mode-locking.html

"graphene microfiber composite structure through optical deposition method, which achieves all-fiber structure and solves problem of low modulation depth saturable absorbers... graphene mode-locked fiber laser constructed in negative dispersion region, and output characteristics of 2 switchable mode-locked pulses in graphene mode-locked fiber laser, the effects of pump power and polarization state on bright dark soliton pairs, and dual-wavelength tunable characteristics were studied... fiber lasers"

Related:

Researchers create class of tiny polarization structures called solitons
https://phys.org/news/2023-07-class-tiny-polarization-solitons.html

Looking deeper into graphene using rainbow scattering
https://phys.org/news/2023-07-deeper-graphene-rainbow.html